GENETIC EVALUATION OF CANADIAN DAIRY BULLS FOR MILKING SPEED WITH AN ANIMAL-MODEL

Bull proofs for milking speed were computed under an animal model for five dairy breeds. Data were subjective scores on first lactation cows from all milk recording agencies across Canada. There were 1411 Holstein, 171 Ayrshire, 85 Jersey, 31 Guernsey, and 17 Brown Swiss bulls that received official evaluations. Bull proofs were expressed on a linear scale from 1 to 9, where 9 designated bulls with the fastest milking daughters. The biological significance of these proofs was investigated using 6965 weekly cow records of total milking time, average flow rate, and peak flow. Data were on 119 Holstein cows by 41 officially proven sires. increases in proofs of 1 point on the linear scale were associated with decreases in total milking time of 20 s and increases of 64 g min-1 and 140 g in average and peak flow, respectively.